Many rotary machines use a Roots type of blower, having two lobed rotors. Alternating with the lobes of each rotor are channels. Each lobe engages a corresponding channel of the other rotor as the rotors are rotated. In order to pump air, the rotors are rotated causing the lobes and channels of the opposing rotors to mesh. During this meshing action, as well as air being pumped from an inlet to an outlet, fluid is squeezed out of the area between the lobes and channels of the opposing rotors. Also, as the lobes leave the channels, air is drawn into the channels. There is thus a continuous pumping action of air entering and leaving the channels, which results in excessive heat generation. As the air is compressed its temperature rises. This rise in temperature, combined with frictional wear, tends to create premature wear and ultimate failure.
Roots blowers are used on a variety of internal combustion engines. In particular, they are commonly used on diesel engines for trucks. For such uses, they can provide adequate supercharging. Being a simple, robust unit, they are relatively reliable.
However, as is known, Roots blowers have limitations. There is no direct compression of air in the blower, and they are best suited for developing relatively low pressures.
Such Roots type blowers developed for trucks have been adapted for cars in so-called drag racing. For this purpose, it is necessary for the engine to develop a high level of power for a short time. To this end, the Roots blowers are rotated at relatively high speeds. This produces inefficiencies, and in many cases leads to premature failure of the blower, as it is overstressed. This type of Roots blower is made from cast aluminum with tight tolerances. At high loadings, the rotors can deflect to contact the casing causing wear.
Another type of pump used is the rotary vane pump, an example of which is disclosed in U.S. Pat. No. 4,212,603, issued July 15, 1980. This pump employs a single vaned rotor, rotating within a housing. The rotor is adjacent to the housing during a portion of the rotation. The vanes slide in slots and are guided on bearings about a cam to contact the housing at all times.
Parts of this structure have typically been made from metal components. When the pump is required to be used at high speeds a great deal of wear can occur between the various components.
Accordingly, it is seen that there is a need for an improved rotary machine which minimizes wear of the components. Further, for such uses as supercharging, it is desirable that the mechanism should not require the use of lubricating oil mist or the like.